Drip irrigation impacts on the root zone soil environment and enrichment characteristics of heavy metals in soybean

Soil heavy metal pollution seriously endangers the soil ecological environment and food safety production. In this study, drip irrigation tests with four irrigation frequencies were conducted by controlling the lower limit of the soil matric potential (D1: -10 kPa; D2: -20 kPa; D3: -30 kPa; D4: -40 kPa). Through comparison with traditional surface irrigation, the effect of drip irrigation on the root zone soil environment under heavy metal pollution and the mechanism through which drip irrigation influences soybean heavy metal enrichment characteristics were explored. The conclusions are as follows. (i) Drip irrigation can improve the root zone soil environment of soybean under combined Cd, Pb and Cr(VI) pollution and is conducive to the recovery of bacterial community structure. (ii) Compared with surface irrigation, drip irrigation reduced the contents of Cd, Pb and Cr(VI) in the root zone soil, with maximum reductions of 34.88% (D1), 31.35% (D2) and 34.20% (D2), respectively. (iii) Drip irrigation increased the accumulation of Cd, Pb and Cr(VI) in soybean. However, compared with surface irrigation, drip irrigation changed the distribution of Cd, Pb and Cr(VI) in soybean organs so that more Cd, Pb and Cr(VI) were stored in roots and significantly less Cd and Cr(VI) were stored in seeds, with maximum reductions of 16.62% (D2) and 19.49% (D2), respectively. These results can be used to develop a new strategy for the prevention and control of soil heavy metal pollution.